import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static long sumOfGroup(int k) {
        int c=0;
        long sum=0;
        for(int x=1;x<=k;x++)
        { 
            c++;
            int ar[]=new int[c];
            for(int y=1;y<=c;y++)
            {
                
               ar[y-1]=c;
                c++;
            }
            if(x==k)
            {
               for(int y=0;y<=c;y++)
               {
                   sum=sum+ar[y];
               }
            }
        }
               return sum;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int k = in.nextInt();
        long answer = sumOfGroup(k);
        System.out.println(answer);
        in.close();
    }
}